RU2402864C1 - Adjustable transistor reducer of three-phase asynchronous motor supplied power to from single-phase mains - Google Patents

Abstract

FIELD: electricity. ^ SUBSTANCE: adjustable transistor reducer of a three-phase asynchronous motor supplied power to from single-phase mains contains two semiconductor valve groups (diode- and transistor-based accordingly) that are intended for connection to Y-connected stator windings of the motor. The first valve group is represented by a diode rectifier bridge whose first alternating voltage input is connected to the feeding mains phase while the second alternating voltage input is connected to the feeding mains neutral. The second valve group is composed of six transistors meant to provide for windings vector and algorithmic switching, two p-n-p and n-p-n structured transistors per motor winding. Collectors of p-n-p structured transistors are connected to those of n-p-n structured transistors and to stator windings beginnings Emitters of p-n-p structured transistors are connected to the rectified voltage pole of the diode bridge while those of n-p-n structured transistors are connected to the minus of rectified voltage of the diode bridge. ^ EFFECT: improvement of energy indices, reliability and cost-effectiveness and reduction of overall dimensions. ^ 7 dwg

Description

The present invention relates to single-phase-three-phase discrete low-frequency frequency converters driven by a single-phase network, and can be used in an electric drive to power asynchronous three-phase and synchronous motors.

Known three-phase low-frequency semiconductor frequency converter, driven by a three-phase network, formed from three three-phase zero thyristor rectifiers. The outputs of the thyristor rectifiers are designed to connect to the inputs of the three stator windings included in the star. In this case, the thyristor anodes are connected to the corresponding phases of the three-phase network, and the cathodes are interconnected, forming a zero point, which is connected to the input of the corresponding winding. The outputs of the stator windings are designed to connect to zero the supply network (Bernstein I.Ya. Thyristor frequency converters without a DC link / I.Ya. Bernshtein. - M.: Energy, 1968. - P. 42, Fig. 2-10a.) .

The main disadvantages of this low-frequency semiconductor frequency converter driven by a three-phase network are low reliability and increased dimensions due to the use of a large number of thyristors.

Closest to the proposed invention by its technical nature and the achieved result (prototype) is a low-frequency frequency converter of an induction motor, the stator windings of which are connected to a star containing three semiconductor valve groups. The first valve group is made on the basis of three diodes, the cathodes of which are designed to be connected to the plus of a 300 V DC direct current network and a zero wire, which is connected to the outputs of three stator windings. The second valve group contains three bipolar transistors, the emitters of which are designed to connect to the negative of the DC supply network. The third valve group contains three field-effect transistors, the sources of which are connected to the corresponding anodes of the three diodes forming the first valve group, and the drains are connected to the common negative of the DC supply network. The collectors of the three bipolar transistors of the second valve group are connected to the corresponding gate of the field-effect transistors, as well as through 9 V resistors, and the emitters of the three bipolar transistors are designed to connect through the sources of the field-effect transistors to the corresponding stator motor windings. Thus, the converter is made on three field-effect transistors, three bipolar transistors and three diodes (Dubrovsky A. Improvement of the speed controller of three-phase asynchronous motors / Dubrovsky A. // Radio. - 2002. - No. 11 - P.41).

The main disadvantages of the described low-frequency semiconductor frequency converter are the reduced energy performance of an induction motor due to the presence of a neutral wire connected to the stator winding, the use of a stabilized DC power source, the presence of a constant component in the network supplying the motor windings, since the current flows through the windings in only one direction , which causes the magnetization of the stator windings, reduced reliability, increased dimensions and cost The need to use a large number of transistors for different voltages, diodes and an additional source of constant voltage and the absence of potential isolation between voltages 300 V and 9 V.

In the present invention, the problem of increasing energy performance, reliability, efficiency, as well as reducing the dimensions of the device.

To solve the problem in an adjustable transistor gearbox of a three-phase asynchronous motor, powered by a single-phase network containing a semiconductor first valve group based on diodes and a second valve group based on transistors designed to connect to the stator windings of the motor connected to a star, according to the invention, the first valve group based on diodes made in the form of a diode single-phase rectifier bridge having a first AC voltage input, designed for connecting to the phase of the mains supply, a second AC input intended to be connected to zero of the mains supply, the first output being the plus of the rectified voltage, and the second output being the minus of the rectified voltage. The second valve group is made up of six transistors designed to provide vector-algorithmic switching of the windings, two transistors of structures p-n-p and n-p-n connected to one stator winding of the motor. The collectors of transistors of structure p-n-p are connected to the collectors of transistors of structure n-p-n and to the beginnings of stator windings, while the emitters of transistors of structure p-n-p are connected to the plus of the rectified voltage of the diode bridge, and the emitters of transistors of structure n-p-n are connected to the minus of the rectified voltage of the diode bridge.

The increase in energy performance is due to the exclusion of a constant component in the power circuit of the stator windings due to the flow of current in two directions along the stator windings.

Improving reliability, efficiency and reducing the size of the adjustable transistor gearbox of a three-phase asynchronous motor powered by a single-phase network is due to both the simplification of the power control system due to the reduction in the number of power switching elements and the absence of a neutral wire in the stator circuit, as well as the absence of an additional low-voltage voltage source potentially associated with a voltage source of significantly greater magnitude.

The invention is illustrated by drawings, in which Fig. 1 is a circuit diagram of the proposed adjustable transistor gearbox of a three-phase asynchronous motor powered by a single-phase network, in Fig. 2 is a vector rotation diagram consisting of three fixed positions of the magnetic flux of the stator field, in Fig. 3 - a vector diagram of rotation, consisting of four fixed positions of the magnetic flux of the stator field, figure 4 is a vector diagram of rotation, consisting of six fixed positions agnitnogo stator field flux; figure 5 - phase-by-phase change in magnetic flux in the stator windings in accordance with the vector diagram shown in figure 2, figure 6 - phase-by-phase change in magnetic flux in the stator windings in accordance with the vector diagram shown in figure 3, .7 - phase-by-phase change in the magnetic flux in the stator windings in accordance with the vector diagram depicted in figure 4.

In addition, the drawings show the following:

- f - phase;

- 0 - zero;

- + - plus a direct current source;

- - - minus a direct current source;

- I, II, III, IV, V, VI - consecutive fixed positions of the magnetic flux of the stator;

- U network = f (t) - change in supply voltage in time;

- Upr = f (t) is the rectified network voltage;

- A, B, C - stator windings of the motor;

- VT1-VT6 - transistors;

- arcuate lines with arrows - the direction of the changing magnetic flux of the stator field of the motor;

- straight lines with arrows - directions of the magnetic flux and current in the stator windings.

An adjustable transistor gearbox of a three-phase asynchronous motor, powered by a single-phase network, contains a semiconductor first valve group based on diodes and a second valve group based on transistors designed to be connected to the stator windings of the motor connected to a star. The first valve group based on diodes is made in the form of a diode single-phase rectifier bridge, in which the first AC input is designed to connect to the phase of the supply network, the second AC input is designed to connect to zero supply network, the first output is the plus of the rectified voltage, the second output is minus the rectified voltage. The second valve group is made up of six transistors designed to provide vector-algorithmic switching of the windings, two transistors of structures p-n-p and n-p-n for each motor winding. The collectors of transistors of structure p-n-p are connected to the collectors of transistors of structure n-p-n and to the stator winding. The emitters of transistors of the p-n-p structure are connected to the positive DC output of the diode bridge, i.e., to the plus of the rectified voltage, and the emitters of transistors of the p-n-p structure are connected to the negative DC output of the diode bridge, i.e. to the minus of the rectified voltage.

In this case, only p-n-p or n-p-n transistors can be used, including them accordingly.

An example of the implementation of an adjustable transistor gearbox of a three-phase asynchronous motor, powered by a single-phase network assembled on transistors.

The device contains a semiconductor first valve group, made in the form of a diode single-phase rectifier bridge 1, in which the first AC input is designed to connect to the phase of the supply network, the second AC input is designed to connect to zero supply network, the first output is the plus of the rectified voltage, the second output - minus the rectified voltage, and a semiconductor second valve group made on transistors 2, 3, 4, 5, 6, 7 (VT1, VT2, VT3, VT4, VT5, VT6). Transistors 2, 4, 6 (VT1, VT3, VT5) have a p-n-p structure, and transistors 3, 5, 7 (VT2, VT4, VT6) have a n-p-n structure.

The positive DC output of the diode bridge 1 is connected to the emitters of transistors 2, 4, 6 (VT1, VT3, VT5). The negative DC output of the diode bridge 1 is connected to the emitters of transistors 3, 5, 7 (VT2, VT4, VT6). The collector of transistor 2 (VT1) is connected to the collector of transistor 3 (VT2) and connected to the beginning of the stator winding 8 of the motor (winding A). The collector of transistor 4 (VT3) is connected to the collector of transistor 5 (VT4) and is connected to the beginning of the stator winding 9 of the motor (winding B). The collector of transistor 6 (VT5) is connected to the collector of transistor 7 (VT6) and is connected to the beginning of the stator winding 10 of the motor (winding C). The ends of the windings 8, 9, 10 (windings A, B, C) of the motor are connected to a star (Fig. 1).

Adjustable transistor gear three-phase induction motor, powered by a single-phase network, operates as follows.

To obtain a rotating magnetic field by the method of vector-algorithmic lowering the frequency of the stator winding, it is necessary to turn on transistors in a certain sequence.

To ensure rotation of the stator field in the sequence I-II-III, shown in figure 2 by a vector diagram of the rotation of the stator field (fixed position of the magnetic flux), it is necessary to turn on transistors 2, 3, 4, 5, 6, 7 (VT1, VT2, VT3 , VT4, VT5, VT6) as follows:

in the I half-period of the rectified voltage (figure 5) - simultaneously VT1, VT4 - I position of the stator field vector;

in II the half-period of the rectified voltage (figure 5) - simultaneously VT3, VT6 - II position of the stator field vector;

in III half-period of the rectified voltage (Fig. 5) - simultaneously VT5, VT2 - III position of the stator field vector.

To ensure rotation of the stator field in the sequence I-II-III-IV shown in Fig. 3 by the vector diagram of the rotation of the stator field (fixed position of the magnetic flux), it is necessary to turn on transistors 2, 3, 4, 5, 6, 7 (VT1, VT2 , VT3, VT4, VT5, VT6) as follows:

in the I half-period of the rectified voltage (Fig.6) - simultaneously VT1, VT4 - I position of the stator field vector;

in II the half-period of the rectified voltage (Fig.6) - simultaneously VT3, VT6 - II position of the stator field vector;

in III half-period of the rectified voltage (Fig.6) - simultaneously VT3, VT2 - III position of the stator field vector;

in IV half-period of the rectified voltage (Fig.6) - simultaneously VT5, VT4 - IV position of the stator field vector.

To ensure rotation of the stator field in the sequence I-II-III-IV-V-VI, shown in Fig. 4 by the vector diagram of the rotation of the stator field (fixed position of the magnetic flux), it is necessary to turn on transistors 5, 6, 7 (VT2, VT1, VT3 ) in the following way:

In the I half-period of the rectified voltage (Fig.7) - simultaneously VT1, VT4 - I position of the stator field vector,

in II the half-period of the rectified voltage (Fig.7) - simultaneously VT1, VT6 - II position of the stator field vector,

in III half-period of the rectified voltage (Fig.7) - simultaneously VT3, VT6 - III position of the stator field vector,

in IV half-period of the rectified voltage (Fig.7) - simultaneously VT3, VT2 - IV position of the stator field vector,

in V the half-period of the rectified voltage (Fig.7) - simultaneously VT5, VT2 - V position of the stator field vector,

in VI half-period of the rectified voltage (Fig.7) - simultaneously VT5, VT4 - VI position of the stator field vector.

In addition, to change the frequency, one half-wave of the supply voltage can be skipped on one cycle of the vectors, but two, three, and so on. The sequence of turning on the transistors when passing on the same clock switching vectors of two and three half-waves of the supply voltage are similar to those described above (see Fig.2-7). If necessary, the reverse changes the algorithm of the transistors.

Thus, the present invention can be used in a single-phase network for adjusting the speed of household appliances having a three-phase asynchronous squirrel-cage motor, with high reliability and efficiency and small dimensions.

Claims (1)

Adjustable transistor gearbox of a three-phase asynchronous motor, powered from a single-phase network, containing a semiconductor first valve group based on diodes and a second valve group based on transistors designed to connect to the stator windings of the motor connected to a star, characterized in that the first valve group based on diodes made in the form of a diode single-phase rectifier bridge having a first input of alternating voltage, designed to connect to the phase of the supply network and, the second AC voltage input, designed to connect to zero power supply, the first output, which is the plus of the rectified voltage, and the second output, which is the minus of the rectified voltage, the second valve group is made of six transistors designed to provide vector-algorithmic switching of the windings, two transistors of structures pnp and npn connected to one stator winding of the motor, while the collectors of transistors of the structure pnp are connected to the collectors of transistors of the structure npn to the beginnings of the stator windings, while the emitters of transistors structure p-n-p are connected to the positive rectified voltage of the diode bridge, a transistor structure emitters n-p-n are connected to the negative terminal of the rectified voltage of the diode bridge.

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